The present invention relates to an apparatus and a process for separating, by coalescence, the disperse phase of an emulsion from the dispersion phase of the emulsion.
More particularly, the present invention is directed to an improvement of the invention disclosed in U.S. patent application Ser. No. 890,664, filed Mar. 27, 1978, owned by the Assignee of the present application, now abandoned.
The invention disclosed in U.S. application Ser. No. 890,664, filed Mar. 27, 1978, discloses a process and an apparatus for separation by coalescence of the disperse phase from the dispersion phase of an organic emulsion, wherein an emulsion to be treated is passed successively upwardly through three zones superposed above one another in a single chamber. Raw water containing a preliminarily destabilized emulsion is passed continuously upwardly through a lower destabilizing area, whereat the emulsion is destabilized and caused to flow uniformly toward the filtering and coalescence area. The thus destabilized emulsion is then continuously passed upwardly through the filtering and coalescence area, which contains coalescence material, whereat the disperse phase of the emulsion is attracted in droplet form to the coalescence material such that the droplets grow in size by coalescence during upward passage of the emulsion through the filtering and coalescence area. The thus coalesced emulsion is then continuously passed upwardly into the flotation and separation area, whereat the coalesced droplets of disperse phase separate by flotation from the dispersion phase of the emulsion. The disperse phase and dispersion phase are then withdrawn by separate withdrawal mean from the chamber.
Periodic cleaning of the coalescence material is accomplished automatically as a function of the degree of retention thereby of matter in suspension filtered out from the emulsion. Cleaning includes a washing operation involving passing washing liquid and gas upwardly through the destabilizing area and the filtering and coalescence area, followed by a rinsing operation involving passing cleaning liquid only upwardly through the destabilizing area and the filtering and coalescence area. The washing and rinsing liquid is withdrawn from the chamber at a level above the coalescence material but below the flotation and separation area.
In the process and apparatus of U.S. application Ser. No. 890,664, filed Mar. 27, 1978, the flotation area is disposed above the filtering and coalescence area, with the area of separation between the disperse and dispersion phases of the emulsion having a surface area equal to that of the coalescence area. Therefore, if the liquid, for example water, has a very high degree of pollution, that is if the emulsion to be treated has a high level of disperse phase, the flotation surface area may be inadequate, with the result that the flotation area will become rapidly saturated with the disperse phase. For example, if the emulsion to be treated is an oil-water emulsion, and if the emulsion contains a high level of oil, then the surface area of the flotation area may be insufficient to accommodate a given flow of emulsion to be treated, with the result that the flotation area will become rapidly saturated with the disperse phase, i.e. oil.
In order to effectively treat desired emulsion flow rates having a high degree of pollution or disperse phase, it has been necessary to construct systems according to U.S. application Ser. No. 890,664, filed Mar. 27, 1978, as high as seven meters and having a floor load as great as eight tons per square meter. It will be apparent that such undesirably great heights and resultant great floor loads will present a considerable number of difficulties in utilization of the system, particularly on installations such as offshore platforms.
Additionally, it is known to use horizontal filtration and coalescence devices wherein the emulsion to be treated is percolated either vertically upwardly or crosswise. Such known devices however have various disadvantages. Such percolation filter devices having vertically upward flow do not satisfactorily prevent the disperse phase from being entrained in the dispersion phase, i.e. free oil becomes entrained to an unacceptable extent in the treated water. Such known crosswise or sidewise percolation filters are extremely difficult to satisfactorily clean.